WASHINGTON -The Supreme Court will hear oral arguments today in an important case that will determine whether the police can arrest someone merely because the person refuses to identify himself.

In a friend-of-the-court brief filed in Hiibel v. Sixth Judicial Circuit of Nevada, the American Civil Liberties Union urged the Justices to rule that Larry "Dudley" Hiibel's refusal to identify himself to the police should not, by itself, establish probable cause for arrest.

"Hiibel was arrested for the crime of remaining silent," said ACLU Legal Director Steven R. Shapiro. "However, Nevada cannot criminalize what the Constitution protects. And because Nevada has never claimed any other basis for his arrest, its actions violate the Fourth Amendment's ban on unreasonable searches and seizures."

At issue is the May 2000 arrest of Hiibel, a 59-year-old rancher from Humboldt County, Nevada, who repeatedly refused to identify himself when questioned by a sheriff's deputy. The deputy was investigating a report that an individual had been observed striking a female passenger in a truck. Hiibel was never charged with that crime. Instead, he was arrested and ultimately convicted solely because he would not give his name to the police.

Ruling on Hiibel's challenge to the arrest, the Nevada District Court determined it was "reasonable and necessary" for the officer to ask for Hiibel's identification, and asserted that the public interest in requiring Hiibel to identify himself outweighed his right to remain silent.

A divided Nevada Supreme Court upheld Hiibel's conviction, with three justices dissenting. Among other things, the dissenters pointed out that the same law used to convict Hiibel had previously been declared unconstitutional by a federal appeals court with jurisdiction over Nevada.

"What the majority fails to recognize," the dissenting justices concluded, "is that it is the observable conduct, not the identity, of a person, upon which an officer must legally rely when investigating crimes and enforcing the law."

Key to the ACLU's brief is an analysis of the limits of a 1968 Supreme Court ruling, Terry v. Ohio, which allows police to "stop and frisk" suspects under certain limited circumstances. According to the ACLU brief, an individual subjected to a Terry stop cannot be compelled to answer questions. "Rather, this Court has repeatedly recognized that an individual has an absolute right under the Fourth Amendment not to respond to questions posed to him by a law enforcement officer," the brief said.

The ACLU urged the Justices to not only strike down the Nevada law, but also to uphold the limitations on police stops imposed by the Court in Terry. "The alleged benefits of a requirement that a person subject to a Terry stop identify himself...is substantially outweighed by the individual's countervailing interest in privacy and security," the ACLU said in its brief.